Electromagnetic switch



E. P. OswALD ELECTROMAGNBTIC swITcH Filed March 13. 1920 April 26 1927.

Patented Apr.- 26, 1927.

UNITED STATES 1,625,820 PATENT OFFICE.

EARL P. OSWALD, F DETROIT, MICHIGAN, ASSIGrNOIR., BY MESNE ASSIGNMENTS, TO THE HOOVER COMPANY, OF NORTH CANTON, OHIO, A CORPORATION OF OHIO.

ELECTROMAGNETIG SWITCH.

Application tiled 'March 13, 1920. Serial No. 365,618.

This invent-ion relates to clect1o-inagnetic switches of the solenoid type, and the object is to provide a solenoid having an iron core which normally iloatsin mercury, energiza- 5 tion of the magnet coil by ay iiow of electric current of predetermined amperage causing the core to become wholly or partially immersed raising the level of the, mercury and thereby closing an electric circuit and a drop l0 in the amperage belouY the predetermined amount permitting fthe core to rise and the resulting fall in level of the mercury breaking the circuit. Another object of the invention is to [n'ovide a solenoid switch ot l5 the. character stated adapted to make. or break a circuit through a mercury body upon energization or de-energization of the solo lnoid. A further object is to secure a construction simple and inexpensive in character and to provide a switch mechanism having practically no liability whatever to become inoperative and further to Aprovide a` switch having no mechanically operated parts for mak-ing and breaking the circuit to be` controlled. Electro-magnets of the solenoid type have heretofore been utilized to move a switch arm into or -out of contact with terminals of a circuit. Usually in such construction a spark passes from a terminal 30 to the switch arm on the breaking of the circuit preventing the use of such switch in the presence of an explosive gas for instance.

and due to the factthat switches of this character become readily corroded and bccollie practically inoperative through the adhesion of the mechanically'movable par-ts with the contact members, such former construction is unadapted for use in places dificult of access as'` for instance within a ,sealed chamber in which it may be necessary to place the switch device. VTherefore, an object oftthis invention as heretofore stated is to provide aconstruction in which such mechanically movable parts are eliminated thereby avoiding the inefficiencies of such former construction and alll liability of the device becoming inoperative through corrosion and to provide a construction avoi ding the production of an electric arc exposed to atmosphere thereby permitting the device to be used in the presence of an explosive gas or in the presence of a gas of a character that would corrode the usual contact members of an electric circuit. An additional object is to provide an electro-magnet of the solenoid type in which the core member is practically immovable by influence of the current passing through the coil of the solenoid', the amperage of which is less than a predetermined amount. A further feat-ure ot' construction consists in the provision of means whereby the core may be made to respond to the influence of current of a greater or a. less amperage. These and other objects and the several novel features of the invention are hereinafter more fully described and claimed, and the preferred form of construction of an electro-magnet embodying my invention is shown in the accompanying drawings in which- 70 Fig. 1 is a cross section through the magnet `taken on line 1-1 of Fig. 2. l v

Fig. 2 is a vertical section ot the magnet taken on line 2-2 of Fig. 1.

Fig. 3 is a detail in section showing a 75 vmercury cell, the section being taken-online of Fig. 1. The device consists of a hollow body 1 formed of insulating material provided with an annular recess 2 to receive the/coil 8 of wire 3, which coil is to be understood as being connected in an electric circuit. A chamber 4 is provided centrally in this body in which a soft iron core 5 of the fsolenoid may reciprocate. This central chamber 4 is 35 provided with longitudinal grooves 6 the faces of which are open to the chamber. There are tour of such grooves shown caid the core 5 very closely fits the walls of the chamber between the said grooves 6 being 90 suiiiciently close to prevent a flow of mercury between the wall and core from one of the wells to the other around the core and still permit the core to freely move in the chamber under intiucnce of electric current passing through the coil.

Some of the grooves 6, as shown in Figs.

.1 and 2, extend only about half the len th of -l plate 11 which may electric circuit to be controlled is to be connected with these terminals of which there may be one or more depending upon the character of circuit to be controlled. The grooves and central chamber of the body are closed at the to by means of a cover be sealed in position by shaping the cover to provide a groove in which a Asealing substance 12 may be inserted. By this construction described the interior of the body is completely sealed to atmosphere.

A particular use of this solenoid switch provided with the three terminals here shown is disclosed in my lpending application Serial No. 358,721, liled February let, 1920, showing the device utilized as a motor control apparatus. The device, however, may be used in various ways wherever a circuit is to be closed or opened as may be readily understood by those familiar with the art.'

There is a body of mercury provided 1n the chamber 4 as shown articularly in Fig. 2 which body occupies tie groove 6 at the lower end and the lportion of the chamber directly beneath the core 5. This core is 4 made hollow as shown so that it readily floats in the mercury and when immersed throughthe flow of the necessary current through the'coils 3 will, upon breaking of the circuit or upon a drop in/amperage occurring below that sufficient to cause an immersion' of the core, upon its release quickly raise in the mercury to normal floating position. A solid iron core may be used but has been found somewhat sluggish in action but, by making the core hollow as stated, a

.- greater buoyancy and rapidity o'f action of the core is secured upon release from the 1nluence of the current through the coil. l

It will also be noted that, by making the core hollow as shown, and providing a` threaded plug 13 therefor, 'a greater. o1- less buoyancy may be secured by varying the length of the plug. The purposeof this is to provide a core that, with a certain number of ampere turns in the coil 3 and thus of. definite magnetic influence, will respond only upon flow of current Vof certain amperage and thus the electro-magnet may be standard as to size and quantity of copper in the coil and be made to suit various. conditions by varying the buoyancy of the core so that the core will be rawn, downward into the mercury under a greater or less magnetic iniuence.

e core is preferably of soft iron and normally floats above the center of the coil 3 as shown in Fig. 2 so that the core, under the magnetic influence, tends to move downward to position centrally of the coil. This movement downward displacesthe mercury below the core and causes mercury to rise -in the grooves 6, the quantity ofA mercury and displacement of the core being such that the rise in the grooves 6 is sufficient to cause the same to flow over the walls 9 to contact with the bodies of mercury in the pockets 8 and thus all of the pockets and the termi- 70 nals therein are placed in electrical contact through the body of mercury. A greater or less number of terminals may be utilized than is here shown, the arran ement shown being simply illustrative of t e method of providing terminals for one or more of the pockets and, depending upon the circuits to be controlled, a greater or less number ofY pockets may be provided without departing from the spirit of this invention.

Evidently the core 5 will remain immersed, partially or wholly depending upon its length, and weight during the interval in which'there is a flow of current through the coil 3 of an amperage suicient to hold the same in such position. Upon a breaking of the circuit through the coil 3 or a decrease in amperage of current below that needed to overcome the buoyancy of the core, the core will rise and the circuit between the several terminals willbe broken due to the fact that the fall of mercury resulting from the rise of the core in its chamber se arates the main body of the mercury from t at in the pockets and thus a quick break of the circuit is secured due to the buoyancy of the core in the mercury. v

It is`to be understood'that this device may be made of any size desired having any desired number of ampere turns in the coil 3 and corresponding size of core and mercury well. It is further to be noted that an electric spark will pass between the mercury in thepockets and the main body of Ithe mercury as the same breaks across the ydividing -wall 9 and that no detrimental effeet is produced by the spark for the reason that, although a slight amount of mcrcuiy may become vapor-ized the same will condense on the walls in the upper part ofY the several grooves and thus is not lost. It is further to be observed that, by sealin the chambers to atmosphere, no detrimenta oxidation of the mercury may take lplace inasmuch Yas the oxygen remaining. 1n the upper part of the grooves and central ,chamber will be soon exhausted due to passage of the electric spark between the pockets and the main body of mercu Thereafter no further oxidation may ta e lplace. If desired, Athe chamber may be il ed with a gas incapable of chemically combining with the mercury.

In some instances the main body of mercury may be continually in electrical contact with r,one terminal of the controlled' circuit lll vas indicated at 14 in Fig. 2, the other terminal of which would occupy a position simio lar tothat of the terminal 10. However, I preferably provide the terminals of the 13 controlled circuit in the pockets above the normal level ofk the mercury body 'as heretof ore described.

From the foregoing description it is evident that the device is simple and inexpensive in construction and is very efficient in operation which is a fault ot .former types ol solenoid switches heretofore used in controlling an electric circuit. It. is further to -be noted that a solenoid of this type may be inserted directly in the controlled circuit even though the circuit be carrying current of a high amperage as there are no metal4 contact points or members which are liable yto become fused and no mechanical parts that may stiel; or refuse to operate and further, d'ue particularly to the fact that the electric spark occurring on the breaking of the controlled eircuitis produced within a sealed chamber, the solenoid may be placed leven in the presence of an explosive gas or one that is corrosive in eltect. After the several parts have been` assembled -and the wires` connected with the termina-ls, the whole device including the terminals and end ot' attached wires may be cast in a block of insulating material covering the terminals kas suggested by dotted lines in Fig. 2.

'Vhen so insulated the solenoid switch may be placed in water or in the presence of any fluid that would ordinarilyprevent operation of a solenoid of previous known types having movable switch elements.

Having thus fully described my invention, what I claim and desire to secure ,by Letters Patent ot the United States is-.

l. In a solenoid'magnet, a body having a central chamber, a body of niercury in the chamber, a soft iron core sustained in normal position by the mercury, said core having a hollow longitudinal chamber, a threaded'plug closing the chamber and adapted to be turned to a greater ordess extent into the chamber to vary the buoyancy of the core,

and a coil of a predetermined number of.-

turns about the lower end of the body, the center of which is below the center of the core when in normal position, the buoyancy of the core detern'iining the amperage o current required to actuate the same. i

2. In an electro-magnetot the solenoid type, a body ot insulating material having a central longitudinal chamber, a magnet coil provided about the llower end of the body and chamber therein, a series of pockets formed in the interior wall ofthe chamber, the pockets being open at the'upper, end to the central chamber, an electric` terminal extending through-the body into each ocket,

a body of mercury in the said cham er, arry iron core having an internal chamber of variable volume therein whereby its buoyancy may be varied floating inthe said mercury body, depression of the core through iniuence of the n'lagnet coil causing the body of mercury to rise to overflow into the pockets electrically connecting the said terminals.

An electro-magnetic switch comprisinga body of insulating material having` a central longitudinal chamber, a body ot mercury therein, an iron core of variable buoyancyreciprocablc in the chamber sustained by the mercury, said corehaving a central closed chamber plug forming the closure therefor, the plug adjustable. in the chamber for varying its volume, a series ofpockets open at the upper end to the central chamber of the body and positioned about the interior wall, an electric terminal extending,r into cach pocket, a magnet coil about the lower end of the body and chamber, depression of the iron core by influence of the magnet coils causing the body ot mercury in the chan'lber to rise to the level ot the pockets bringing all of tlie said terminals into electrical contact.

4. An electro-magnetic switch of the solenoid type comprising a body of insulating material having a central longitudinal chamber and grooves provided longitudinally ofthe chamber opening ther-cinto, the upper end of the grooves being of greater depth than the low-er lend providing a shoulder between the two parts, .a pocket provided in thel shoulder thereby providing a wall between the pocket and the lower part of the groove, au electrical terminal extending into the pocket, a body of the mercury in the pocket covering the terminal` and a body of mercury in the bottom of the' chamber, a magnet coil about the lower end of the body and chamber, an iron core normally positioned by the mercury above the center of influence of the coil, energization of the coil to an extent sufficient to overcome buoyancy :of the core causing the core to move downward and the level of mercury ralsedto contact with that 1n the pocket connecting the cation.

EARL P. OSWALD. 

